Chiral centers present either in the dimelamine components of calixarene 1 or in the cyanurate components CA quantitatively induce one handedness (P or M) in the corresponding hydrogen-bonded assemblies 13(CA)6 (de>98 %). The high degree of chiral induction results from the presence of six chiral centers in close proximity (Cα) to the core of the assembly. A much lower level of chiral induction is observed for assemblies with chiral centers that are more remote (Cβ). All diastereomerically pure assemblies 13(CA)6 exhibit very high CD activities (|Δεmax|100 L mol-1 cm-1), in sharp contrast to the low CD activities (|Δεmax|8 L mol-1 cm-1) shown by the free components. The assemblies display spontaneous resolution under thermodynamically controlled conditions (i.e., heteromeric assemblies containing both peripheral R and S centers are not observed. Remarkable assembly behavior is observed if both components 1 and CA are chiral. In general, formation of well-defined assemblies is only observed when both components contain unidirectional information for the induction of either M or P chirality.
|Journal||Chemistry: a European journal|
|Publication status||Published - 2002|
- supramolecular chirality
- Hydrogen bonds
- Noncovalent interactions